Many consumer products in liquid form are sold in smaller containers from which the user periodically pours or dispenses a small amount of the liquid. Typical liquids are shampoo, liquid soaps, dishwashing detergent, soya sauce, mineral oils, etc. Such liquids are sold very competitively and consequently the products are often sold in inexpensive bottles having some form of closure or simple dispensing pump.
The user will periodically require liquid from the container and it would be preferable for the container to be easy to use with no dripping or dribbling. Existing containers of this type exit through a top closure or pump. In the case of a simple closure the user inverts the container to get liquid to flow towards the closure before liquid will emerge. There is therefore a tendency for an apparently empty container to have a significant amount of liquid remaining on the walls of the container.
The pump system is intended to be used with the container supported so that the pump is depressed downwardly with the container providing the reactive load. These structures are very difficult to empty and tend to drip or dribble.
It has been found that the above disadvantages can be largely overcome by the present invention which takes advantage of principles taught in U.S. Pat. Nos. 4,324,349; 4,635,828; 4,645,097; 5,033,653; and 5,427,279 to Kaufman all of which are examples of what have become known as "Kaufman dispensers". These patents teach dispensers which have no moving parts and yet satisfy the requirements of clean dispensing with temperature compensation to permit the dispenser to be subjected to a designed temperature range without significant inadvertent dripping or dispensing caused by temperature variations.
The structures shown in the Kaufman patents have a reservoir for liquid to be dispensed in communication with a main part of the dispenser in the form of a container where the major volume of the liquid is contained. Air is trapped above the liquid in the container under a negative pressure which prevents the liquid flowing from the container into the reservoir and out through a discharge passageway. Dispensing can be initiated in several ways. For instance embodiments are provided in the earlier patents which are caused to dispense by squeezing the container. The resiliently deformable container rebounds to its original shape when squeezing is discontinued so that air is sucked back into the passageway and the container is set up in a new condition of equilibrium.
There are two significant parameters present in such dispensers. Firstly the reservoir is designed to provide space for the liquid level in the reservoir to rise when ambient temperature rises. Secondly the reservoir and discharge structure are designed to provide quick response to the dispensing action. Previous Kaufman patents have described these parameters in detail, but in general it has been found that the parameters work against one another because the response time increases as the temperature compensation volume increases.
Special structures can be used to overcome this problem if needed but such structures are not as effective in smaller dispensers of the present type.
It is therefore desirable to provide a dispenser for smaller volumes of liquid which is ergonomically acceptable and which, in operation, minimizes the effects of the aforesaid conflicting parameters.